1. Field of the Invention
The present invention relates to storage systems, such as but not limited to redundant disk arrays, that use hard disk drives to store data. More particularly, the invention involves methods for reliably detecting power-on-reset events that can result losses of data, and for recovering from such events.
2. Description of the Related Art
A disk drive can experience an unwanted or unexpected power-on-reset (“POR”) event due to various types of anomalies, such as a loose power cable connection, a failing power supply, or a power voltage drop caused by another component. When such a POR event occurs, write data that has been cached by the disk drive but has not yet been written to the magnetic disk media may be lost, especially if the POR event is not detected. One solution to this problem is to disable the write caching feature of the disk drive. For example, some manufactures of disk array systems ship these systems with disk drives that have write caching disabled. This approach, however, can significantly impact the performance of the storage system.